Transcript What adaptation allows CAM plants to live successfully in desert

What adaptation allows CAM plants to live
successfully in desert environments?
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their roots are extensive but shallow,
allowing any rainfall to quickly collect
their stomata are permeable to CO2
and O2 but not water, allowing water
to be retained while photosynthesis
continues
they utilize a cyclic photosynthetic
pathway exclusively and don't
require water as an input for
photosynthesis
they collect and store CO2 at night,
then release it during the day when
light energy is available for
photosynthesis
their thylakoid membranes are
impermeable to water
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One product of the light-dependent reactions
is NADPH; why is NADPH significant?
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it is a photosynthetic waste product
designed to remove surplus hydrogen
and energy-depleted electrons from
the chloroplast
NADPH is a component of electron
recycling; it passes an electron to one
of the pigment molecules
NADPH donates electrons and
hydrogen ions to carbohydrate
synthesis during the light-independent
phase of photosynthesis
the molecule dissociates to form free
oxygen and NADP
NADPH donates hydrogen ions to the
gradient forming in the thylakoid
compartment
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Englemann's studies of photosynthesis
showed that Spirogyra used which colors of
light most effectively?
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violet and yellow
red and yellow
red and violet
blue and yellow
green and yellow
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How can the green color of
most plant leaves be explained?
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green light most effectively supports
photosynthesis; it is absorbed and causes
plants to appear green
excited pigment electrons emit green light
when falling back to their unexcited
energy states
the green wavelengths have the wrong
energy characteristics for photosynthesis
and green light is simply reflected from
the plant's leaves
green light is transmitted by the leaf,
explaining why both the top and bottom of
the leaf appear green
plant leaves reflect both blue and yellow
light; the combination of these colors
appears green to the human eye
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What simple molecule, released during
photosynthesis, changed both the atmosphere and
the biochemistry of life on early Earth?
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carbon dioxide, or CO2
carbon monoxide, or CO
nitrogen, or N2
ammonia, or NH3
oxygen, or O2
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When stomata are closed in a photosynthesizing
plant leaf, the concentrations of CO2 ________
and O2 ________.
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increase, increase
decrease, increase
decrease, decrease
increase, decrease
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During the fall, leaves often become
red or yellow as ________.
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new pigments are added to exploit
the changing quality of light as the
season changes
the chlorophylls break down and no
longer mask the presence of other
accessory pigments
pigments that once reflected the red
and yellow wavelengths now absorb
them
environmental cooling lowers the
electron energies of various
pigments
photosystems damaged by time
permit excited electrons to fall back
to their resting states, releasing their
energy as red and yellow light
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The colors of light visible to the human
eye correspond to ________.
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variations in photon speed
the relative balance between
light's particle-like and wavelike qualities
the wavelengths of the
photons
the composition and mass of
the photons
the angle the light strikes the
human eye
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Carbon that is converted to carbohydrate in
the light-independent pathways comes from
________.
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carbon dioxide
glucose
starch
water
various organic
compounds
produced by
autotrophs
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Biologists hypothesize that the
C3 and C4 pathways ________.
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evolved from the more primitive
CAM pathway as plants adapted to
live in habitats other than moist,
swampy ones
developed in those aquatic plants
that lack stomata
represent photosynthetic strategies
that allowed primitive
photoautotrophs to utilize habitats
where light intensities are very low
evolved as a desert adaptation,
since neither pathway requires water
as a source of photosystem
electrons
evolved at different times in
response to differences in
atmospheric composition
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Cacti display many adaptations for
desert living, including ________.
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stomata that open at
night rather than during
the day
thick surface layers that
limit water loss
succulent leaves
the CAM pathway for
carbon fixation
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Where do the light-independent
reactions occur?
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in the inner chloroplast
membrane
in the thylakoid
in the outer chloroplast
membrane
in the stroma
in the photosystem
complex
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What statement best summarizes the balance
between carbon fixation through photosynthesis
and carbon release through human activity?
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at the present rate of photosynthesis,
the atmosphere will be depleted of CO2
within one million years
photosynthesis currently removes less
CO2 than human activity releases, but
inorganic processes remove the
excess, resulting in stable atmospheric
amounts
the total production of CO2 is precisely
balanced by photosynthesis
since photosynthesis is globally limited
by the availability of CO2, increases
from human activity are quickly
captured by plant growth
human activities release more CO2
than photoautotrophs can fix;
significant atmospheric changes are
possible
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The electrons needed to replace those
transferred from photosystem II are supplied
by ________.
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rubisco
photosystem I
NADPH
water
ATP synthase
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A variety of human activities, including ________,
threatens to reduce the growth of marine
photoautotrophs and disrupt marine food webs.
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enrichment of marine waters
with fertilizers
the introduction of raw
sewage
the disposal of industrial
wastes
the warming of surface
waters
burning fossil fuels
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Earth's earliest photoautotrophs were anaerobic; how did
they adapt to the increasing concentrations of oxygen
created by advances in photosynthesis?
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many were unable to adapt and
simply perished in an early mass
extinction event
some species evolved
chemoautotrophic pathways and
were able to occupy extreme
habitats like sea-floor hydrothermal
vents
the ancestors of most modern
bacteria evolved metabolic pathways
that could detoxify oxygen
some became restricted to
anaerobic habitats such as swamps
and sediments
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Photorespiration, which reduces sugar
synthesis, occurs when ________.
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plant tissues become anaerobic
oxygen concentrations rise
above critical levels and begin
reacting with ribulose
bisphosphate
plants switch from the C3 to the
C4 pathway
oxaloacetate is formed within
the mesophyll cells
stomata open after extended
periods of closure, allowing a
temporary influx of oxygen
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What term is used to describe those
organisms that can make their own food?
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allotroph
autotroph
heterotroph
saprobe
chemotroph
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What statement best summarizes
the light-dependent reaction?
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carbon dioxide and water are
combined to produce sugar and
oxygen
ATP created in the Calvin-Benson
cycle is used to synthesize
carbohydrate
chlorophyll a oscillates between a
reduced and oxidized form
light energy is converted to the
chemical bond energy of ATP
light energy is used to assemble
water molecules from atmospheric
oxygen and NADPH
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The term carbon fixation is used
to describe the ________.
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conversion of organic
compounds into fossilized rock
conversion of organic
compounds into oil and oilrelated products
incorporation of environmental
carbon into stable, organic
compounds
transfer of carbon from one
organic compound to another
incorporation of organic remains
to the sediments forming the
ocean floor
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